Invisible Wall
Max learns how to tell that the wall is down.
Seen in Episode #5: "Now You See Him, Now You Don't"
Kind of device Defence
Organization CONTROL
Used by Maxwell Smart

Impenetrable barrier installed in Maxwell Smart's apartment by the CONTROL lab.

The wall cannot be seen but is impervious to all forms of attack. It is lowered by leaning on a panel on the edge of the desk.

Seen in the following episodes: